Production of hydrogen



Patented Feb. 21, 1939 PATENT OFFICE No Drawing. Application October 5, -1936, Serial No.104,061. In AuStria October 23,1935

Claims. (01. 23 212) Thisinvention relates to the production of hydrogen by reacting a mixture of carbon monoxide and steam, and more particularly to such a process involving the useof an improved catalyst.

It is the object of the invention to provide a method for the manufacture of'hydrogen by the interaction of carbonmonoxide and steam or by eliminating carbon monoxide from gaseous mixtures containing a high'percentage of hydrogen and a relatively low percentage of carbon monoxide such as water-gas, which will be more expeditious and less costly than those heretofore proposed. Other objects and advantages of the invention will be apparent as it is better understood by reference to the following specification in which its details and preferred embodiments are described.

For the catalytical conversion of carbon monoxidewith steam there have been proposed catalysts consisting of a mixture of magnesium oxide, carbon, and alkali carbonate, preferably potassium carbonate. With the aid of these very active catalysts the conversion of the CO proceeds even at temperatures below 500 C. with useful velocities up to'the point at which, practically speaking, complete establishment of the equilibrium is attained. This results in the advantage that in large scale Working a low residual CO content, accordingto the temperature, can be obtained without uneconomically high steam consumption. -When working with these catalysts itis further also possible to effect the conversiornwithout the disadvantage of undesirable secondary reactions such as in particular deposition of carbon and formation of methane, under increased pressure, at the temperatures most favorable for the conversion of CO to CO2 and H2, and thus to effect a saving in reaction space and steam consumption. When-other catalysts, and more particularly the known activated iron oxide catalysts, are used these secondary reactions set in closely below 500 C. and rapidly reach an intolerable scale as the temperature falls.

In accordance with the present invention the conversion of carbon monoxide with steam is carried out with the aid of catalysts which contain, apart from magnesium oxide and alkali carbonate (preferably potassium carbonate) and carbonaceous substances, as a further constituent iron oxide in the form of native iron ores. Red iron ore (micaceous iron-ore, haematite, bloodstone, and the like) occurring in nature contains ferric oxide (FezOz). Iron in the form of ferric hydroxides occur in nature in brown iron ores (limonite containing FB403(OH)6, bog iron ores containing FezO(Ol-I) 4, gothite containing FeO(OH), and the like). Apart from such ores there may also be used for the present method iron ores which yield ferric oxide or ferric hydroxide-under heat, examples of such ores being sideritecontainingFeCOz and magnetite containing Fes04.

It has been found that the efficacy at the favorable working temperature below 500 C. of the known three-component catalysts magnesium oxide-alkali carbonate-carbon is enhanced to a very surprising extent by the accessory effect of iron oxide in the original state of native iron ores, that is to say without being brought into the state of finely divided artificial iron oxide, and that the above-mentioned native iron ores are capable of producing this effect when used in such small amounts that no deposition of carbon or methane formation occurs even when Working under excess pressure and at the lowest applicable temperatures. Moreover, these fourcomponent catalysts also retain undiminished the poison-resisting properties of the known three-component catalysts, more particularly in respect of the commonestcatalyst poison, name-- 1y sulphur, in inorganic ,or organic combination. This state of things shows that the components combine, within the range of proportions here concerned,'to form a new unity having decisive- 1y altered properties.

The quantity of iron oxides in the mixture required to obtain marked enhancement of the catalytical activity of the three-component catalysts in question, depends on the proportions of the other constituents'of the catalyst mass.

Broadly it may be stated that the proportion of iron oxides to-thetotal quantity of MgO +K2CO3 contained in the catalyst should be between 1:30 and 1:2. The iron oxide content should preferably amount to at the most of the entire catalyst mass.

The magnesium oxide used may be in the state of caustic burned or calcined magnesia, or of precipitated magnesia. Instead of adding native iron oxide or ferric hydroxide to the magnesia it is also possible to start with magnesite rich in iron or its transition states to breunerite (MgCOaFeCOa) without any further addition of iron.

The catalyst may for example have the following composition:-

Per cent MgO (in the form of calcined or caustic burned magnesia) 13.5 F6203 (in the form of iron ore) 1.5 Potassium carbonate 15.0 Carbon 70.0

For the production of a catalyst mass of this nature 27 kgs. of the caustic burned magnesia and 3.75 kgs. of dried bog iron ore containing about 80% of ferric oxide are mixed in a pan grinder. After the addition of 140 kgs. of wood charcoal mixing is repeated. There is then added a concentrated solution of kgs. of potassium carbonate and about 30 kgs. of a suitable binding agent (for example wet asphalt), and the mixture passed through a pug mill. The finished mixture is then compressed, and heated at a temperature of about 800 C., with the exclusion of air, for three to four hours. The conversion of the starting gas or gaseous mixture with steam is carried out with advantage by raising the temperature to slightly below 500 C. in the initially encountered zones of the catalyst mass, where the greater part of the carbon monoxide is converted, and allowing the temperature to fall ofi gradually in the succeeding zones, so that the last section at the discharge end of the furnace is kept at a temperature of between 370 and 350 C. When working at normal pressure, under these circumstances, the output in the hottest regions is more than doubled in comparison with a similar catalyst which contains only the slight quantities of iron present from the outset in natural magnesite poor in iron; in the coolest regions, on the other hand, the activity is less. At higher pressures the output in the hottest zone is considerably higher still, and also increases to an appreciable extent in the coolest zone.

I use the term iron oxide in the following claims to include not only oxides but also hydroxides of iron and combinations yielding iron oxide or bydroxide under heat, while the numerical indications refer to ferric oxide (F8203).

I claim:

1. The process of producing hydrogen which comprises causing steam to react with carbon monoxide according to the reaction in the presence of a catalyst consisting principally of a mixture of magnesium oxide, alkali carbonate and carbonaceous substance, and containing a considerably smaller amount of iron oxide in the form of native iron ore, the ratio of the quantity of iron oxide to the total quantity of magnesium oxide and alkali'carbonate in the catalyst being between 1:30 and 1:2.

2. The process of producing hydrogen which comprises causing steam to react with carbon monoxide according to the reaction in the presence of a catalyst consisting principally of a mixture of calcined magnesite, potassium carbonate and carbonaceous substance, and containing as an activator a considerably smaller amount of iron oxide in the form of native iron ore, the ratio of the quantity of iron oxide to the total quantity of magnesium oxide and alkali carbonate in the catalyst being between 1:30 and 1:2.

3. The process of producing hydrogen which comprises causing steam to react with carbon monoxide according to the reaction in the presence of a catalyst consisting principally of a mixture of calcined magnesite, alkali carbonate and carbonaceous substance, and containing as an activator a considerably smaller amount of iron oxide in the form of native iron ore, the ratio of the quantity of iron oxide to the total quantity of magnesium oxide and alkali carbonate in the catalyst being between 1:30 and 1:2 and the iron oxide content amounting at the most to 10 per cent of the Whole of the catalyst mass.

4. A process of producing hydrogen including reacting a mixture of carbon monoxide and steam in the presence of a catalyst prepared from magnesitic material rich in iron by the addition of alkali carbonate and carbonaceous matter, the ratio of the quantity of iron oxide to the total quantity of magnesium oxide and alkali carbonate in the catalyst being between 1:30 and 1:2 and the iron oxide content amounting at the most to 10 per cent of the whole of the catalyst mass.

5. The process of producing hydrogen which comprises reacting a carbon monoxide-containing gaseous mixture rich in hydrogen, and steam in the presence of a catalyst consisting principally of a mixture of magnesium oxide, alkali carbonate and carbonaceous matter, and containing as an activator a considerably smaller amount of iron oxide in the form of native iron ore, the ratio of the quantity of iron oxide to the total quantity of magnesium oxide and alkali carbonate in the catalyst being between 1:30 and 1:2.

FRIEDRICH VON KAHLER. 

